The goal of this research is to improve our understanding of teenage contraceptive behavior in the U.S. Whereas the contraceptive patterns of married couples have been documented in recent years, less is known about contraceptive use during the teen years. These early experiences with contraception may have a long-term impact on subsequent contraceptive behaviors as well as pregnancy impacts during the teenage years. Our research uses two existing national surveys: (1) Cycle III of the National Survey of Family Growth and (2) the Kantner-Zelnik Study of Young Women and Young Men. We contend that since among teens, decisions about contraception may be closely linked to decisions about sexual activity, both types of decisions may be jointly determined. Our analytic approach takes into account this complex aspect of teenage contraceptive decision making. A full understanding of the contraceptive behavior of teens requires knowledge of their sexual patterns, since they are often thought to be sporadic and episodic. After first evaluating the quality of the sex and contraceptive histories provided by the data sets (Specific Aim 1), we focus specifically on the patterns of teenage sexual activity, going beyond the simple age at first intercourse measure, typically used in other studies (Specific Aim 2). In Specific Aims 3 and 4, we analyze the determinants of contraceptive use and method choice at first intercourse (Aim 3) and in the period prior to the survey (Aim 4). We estimate a bivariate probit model using maximum likelihood techniques to take into account the joint dependence of decisions regarding sexual activity and contraception. The determinants include social background characteristics, life course attributes and past experiences with contraception. In Specific Aim 5, we examine the impact of a pregnancy on subsequent contraceptive behavior. In Aim 6, we shift our focus to males and assess the determinants of their contraceptive behavior.